1. Field of the Invention
This invention relates to chemical delivery systems, and more specifically to a chemical delivery system for delivering a liquid chemical to a textile laundering appliance (e.g., a washing machine) located within a semiconductor fabrication clean room.
2. Description of Related Art
It is well known that small particles (i.e., particulates) can cause defects in integrated circuits formed upon semiconductor wafers. Such defects may prevent the integrated circuits from performing their intended functions. For example, a process called photolithography is used to pattern layers of desired materials deposited upon the semiconductor wafers. During photolithography, light passing through a pattern on a mask transfers the pattern to a layer of light-sensitive photoresist deposited over a layer of desired material. Particulates on the surface of the mask or on the surface of the photoresist layer which block or diffuse the light cause imperfect pattern registrations (i.e., imperfect feature formations). The resulting imperfect features formed within an integrated circuit may render the integrated circuit inoperable.
In order to help keep wafer processing areas as particle free (i.e., "clean") as possible, such areas are designated as "clean rooms". Particulates may be present within the air in clean rooms, introduced by processing personnel, suspended in liquids and gasses used during wafer processing, and generated by processing equipment located within the clean rooms. As a result, the air within clean rooms is typically continuously filtered. Liquids and gasses entering clean rooms and used during processing are also filtered, and clean rooms typically exclude portions of processing equipment which generate particulates.
Air "cleanliness" levels of clean rooms are determined by the densities of different sizes of particulates present in the air and are specified using class numbers. The allowable densities of particulates within clean rooms is dependent upon the clean room class numbers and the largest dimensions of the particulates. For example, a class 1 clean room can have only 1 particle with a largest dimension of 0.5 micron in each cubic foot of air, but may have up to 34 particles with largest dimensions of 0.1 micron per cubic foot of air. The required class number for a particular clean room is largely determined by the feature sizes of the integrated circuit devices being produced within the clean room. Portions of many integrated circuits produced today are formed within class 1 clean rooms.
Humans continuously generate large numbers of particulates including dead skin cells and hairs. When working in clean rooms, personnel typically wear low-particle-generating coverings which almost completely envelope their bodies. The clean room garments essentially form filters around the wearers, reducing the number of particulates generated by the wearers which escape into the air. Exemplary garments include overalls and hoods, face masks, safety glasses or goggles, leggings, shoe covers, and gloves. Undergarments such as caps or nets may also be used to keep hair in place under hoods.
Clean room garments must be laundered on a regular basis if they are to remain functional and sanitary. The laundering process must, however, be carried out such that the clean room garments do not become sources of large number of particulates. For example, particles present in the water used to wash the clean room garments, or particles of a laundering agent (e.g., a detergent) added to the water, may become trapped in fibers of the clean room garments during laundering. Such particles may be released into the air during wear of the garments. Improper laundering may also damage the fibers of the clean room garments, causing them to break apart. In this case, small pieces of the fibers may be released into the air during wear.
No matter how carefully the laundering process is carried out, transport of laundered clean room garments through the relatively "dirty" environment between an off-site facility and the clean room presents a particle contamination problem. In fact, the plastic bags routinely used to protect laundered garments are themselves particle generators, rendering them ineffective in protecting clean room garments from the introduction of particles during transit. It would thus be desirable to launder clean room garments in a laundry facility adjacent to or within a clean room facility.
FIG. 1 is a front elevation view of an exemplary washer/extractor 10 for laundering textiles. Washer/extractor 10 may be installed in a laundry facility adjacent to or within a clean room facility. Washer/extractor 10 includes a cylindrical drum mounted within a housing 12 such that a rotation axis of the drum is horizontal. Housing 12 is typically bolted to a floor 15. In order to provide physical isolation for laundered and soiled garments, washer/extractor 10 has a loading side on one side of the drum and an unloading side on the other side of the drum. Soiled garments are loaded into the drum from the loading side and removed from the drum using the unloading side.
During a typical wash operation, soiled garments are placed within the drum, the drum is filled to a certain level with water, detergent is added to the water in the drum, and the drum is rotated about the horizontal axis in order to flush foreign substances from the garments. During a typical extraction operation, the drum is rotated about the horizontal axis at a relatively high rate of speed. Centrifugal force acting radially upon the water retained by the textiles causes the water to leave the textiles and exit the drum through openings (e.g., perforations) in an outer surface of the drum. Six ports 14 are provided on the loading side of washer/extractor 10 for adding liquid chemicals (e.g., detergent) to water in the drum.
A problem arises when washer/extractor 10 is located within a clean room and ports 14 are used to add a liquid chemical (e.g., detergent) to the drum. Any spillage of the liquid chemical adjacent to the loading (or unloading) side constitutes an introduction of contaminants into the clean room. It would thus be desirable to have a chemical washing system including a textile laundering appliance and a chemical dispensing system, wherein the chemical dispensing system delivers a liquid chemical (e.g., detergent) to a textile laundering appliance. The desired textile laundering appliance has opposed loading and unloading sides, and is located within a clean room. The desired chemical dispensing system delivers the liquid chemical to a portion of the textile laundering appliance remote from the loading and unloading sides. Such a chemical dispensing system would reduce the impact of a chemical spill upon clean room operations.